MaxGekk commented on a change in pull request #32056:
URL: https://github.com/apache/spark/pull/32056#discussion_r607605794
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/IntervalUtils.scala
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@@ -834,4 +834,21 @@ object IntervalUtils {
* @return The period of months, not null
*/
def monthsToPeriod(months: Int): Period =
Period.ofMonths(months).normalized()
+
+ /**
+ * Converts an year-month interval as a number of months to its textual
representation
+ * which conforms to the ANSI SQL standard.
+ *
+ * @param months The number of months, positive or negative
+ * @return Year-month interval string
+ */
+ def toYMIntervalString(months: Int): String = {
+ var sign = ""
+ var absMonths: Long = months
+ if (months < 0) {
+ sign = "-"
+ absMonths = -absMonths
+ }
+ s"interval '$sign${absMonths / MONTHS_PER_YEAR}-${absMonths %
MONTHS_PER_YEAR}' year to month"
Review comment:
> The last part "year to month" looks a bit confusing to me
This part conforms to the SQL standard, see:
```
<interval literal> ::=
INTERVAL [ <sign> ] <interval string> <interval qualifier>
<interval qualifier> ::=
<start field> TO <end field>
| <single datetime field>
<start field> ::=
<non-second primary datetime field>
[ <left paren> <interval leading field precision> <right paren> ]
<end field> ::=
<non-second primary datetime field>
| SECOND [ <left paren> <interval fractional seconds precision> <right
paren> ]
<single datetime field> ::= <non-second primary datetime field>
[ <left paren> <interval leading field precision> <right paren> ]
| SECOND [ <left paren> <interval leading field precision>
[ <comma> <interval fractional seconds precision> ] <right paren> ]
<primary datetime field> ::= <non-second primary datetime field>
| SECOND
<non-second primary datetime field> ::= YEAR
| MONTH
| DAY
| HOUR
| MINUTE
<interval string> ::=
<quote> <unquoted interval string> <quote>
<unquoted interval string> ::=
[ <sign> ] { <year-month literal> | <day-time literal> }
```
> What does other DBMS systems do?
For instance, see Oracle
https://docs.oracle.com/en/database/oracle/oracle-database/12.2/sqlrf/Literals.html#GUID-4C258D8F-3DF2-4D45-BE3E-14864DD77100
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